The thumb does not develop properly. The severity varies from a small discreet thumb to complete absence of the thumb (Blauth Classification). Thumb hypoplasia is part of radial deficiencies (such as radial clubhands) and therefore may be associated with syndromes (malformation of other organs). Thus, your baby needs assessment by the pediatrician and geneticist.

It is said that 50% of hand function is due to the thumb. It is therefore imperative to improve or rebuild the thumb, so that the child has a good hand function. Surgery is recommended at around one year of age, since it is the time when children starts thumb-pinch movements.

When a thumb is sufficiently developed, we can improve it and make its function considerably better with surgery. The problems are: difficulty to pinch (less motion, due to absence of muscles), instability (the thumb is diverted out, due to lack of ligaments) and narrow first commissure (space between thumb and forefinger) (Figure 1). By performing a Z plasty in the first commissure (cuts in the skin to enlarge it) and a transfer of a tendon (tendon from the ring finger transfered to the thumb) we can solve these problems and achieve an excellent function.

Figure 1: Hand with thumb hypoplasia. Note that the thumb is unstable and can be diverted out, there is no muscle in the heel of the hand and the first commissure is narrow.

Figure 2: Once the hand is operated, the thumb is stable and can perform a functional pinch.

If thumb is absent or poorly developed, we use the technique of pollicization. It is a surgery technique in which a thumb is created from an existing index finger. We can create a new thumb with excellent performance. (Figure 3 and 4).

Figure 3. The thumb is severely hypoplastic, the reconstruction is meaningless because it will not work. It is preferable to amputate it and perform the pollicization surgery technique, in order to have a normal hand function.

Figure 4. Image of the previous hand, in the operating room just after the pollicization.